javascript范围：在函数后保留全局变量值

Question

When the 'hypotenuse' function is called the value of 'x' changes from 1. Fix it so that 'x' is still 1 in the gobal scope.

  var x = 1;
  var y = 1;

  function hypotenuse(a , b) {
    var cSquared = a * a + b * b;
    x = Math.sqrt(cSquared);
    return x;
  }

  hypotenuse(x, y);

Answer 1

All you need to do to make this happen is redeclare the x variable using var within the function. This is will declare the x variable within the scope of the function, leaving the original, globally scoped x variable untouched:

  var x = 1;
  var y = 1;

  function hypotenuse(a , b) {
    var cSquared = a * a + b * b,
        x = Math.sqrt(cSquared);
    return x;
  }

  hypotenuse(x, y);

Or, using the code style which you originally adopted (splitting out var declarations):

  var x = 1;
  var y = 1;

  function hypotenuse(a , b) {
    var cSquared = a * a + b * b;
    var x = Math.sqrt(cSquared);
    return x;
  }

  hypotenuse(x, y);

For more detailed info on what is happening here, read up on javascript scope

Answer 2

Try this:

  var x = 1;
  var y = 1;

  function hypotenuse(a, b) {
    var cSquared = a * a + b * b;
    var x = Math.sqrt(cSquared);
    return x;
  }

  //console.log(hypotenuse(x, y));
  //console.log('x = ' + x);